The present invention relates to a distance measuring apparatus for measuring a distance to, and a direction of, an obstacle by transmitting light beams at the obstacle, such as an automobile motorbike building and road-side structure, and receiving reflected beams from the obstacle.
An airplane is equipped with a flight recorder for automatically recording the states of flying, such as the altitude and speed, its ascent or descent speed, azimuth and engine output, on a metal foil and storing the recorded data in an impact-/heat-resistant black box. In the case of an accident, the flight recorder, together with a voice recorder, is used for investigation into a cause for the accident.
In contrast to an airplane, an automobile is not equipped with a recorder which corresponds to the flight recorder. Attempts have been made to measure and record a running path of the automobile by utilizing not only the speed, acceleration rate and angular acceleration (yow rate) but also the position information from the GPS based on an artificial satellite. A vehicle-to-vehicle distance measuring apparatus is known which measures a distance to a forwardly positioned vehicle or obstacle and issues collision warning to a driver.
At the collision accident of the vehicle, it is indispensable to clarify a relative position of a driver's own vehicle to the obstacle, together with its direction, just before it collides with the obstacle and, while also utilizing the information such as the driver's speed and acceleration rate (including the angular acceleration rate), decide what action he or she should have taken under this situation. This is indispensable to the investigation into the cause for the accident involved.
A conventionally adopted method comprises grasping a driver's running path together with the speed/acceleration information. In order to clarify a colliding path, the position information from the GPS is not accurate enough and includes nothing at all about a colliding object.
In the case where, at a vehicle/vehicle collision accident, both are equipped with a device capable of measuring/recording their accurate collision path together with their speed/acceleration information, it appears possible to make an investigation into the cause for the vehicle collision. If, on the other hand, one vehicle only has such a device or if the driver's vehicle collides with an obstacle such as the building or roadside structure, various difficulties are encountered.
The colliding distance information can be obtained by a vehicle/vehicle distance sensor. This method is broadly classified into two, that is, a fixed beam method according to which the distance information only is obtained and a scan beam method according to which it is possible to obtain both the distance and direction information.
The former method is not adequate as a means for investigation into the cause for the collision accident because it is not possible to obtain the direction information. The latter method has the advantage of obtaining both the distance and direction information but it is necessary to effect mechanical scanning and it also requires a great amount of time to do so. The latter method is not suitable to the case where the colliding path along which both vehicles are running at high speeds is measured/recorded just before their collision occurs.
Further, according to these methods, the monitoring area extends over a distance of more than 100 m in a forward direction of the vehicle and also covers not only a currently running line but also an adjacent line on the road, that is, inconveniently also covers, as a measuring object, an obstacle low in a risk of collision.